1. Field of the Invention
This invention relates to a recording and reproducing apparatus using a flexible disc as sheet as a recording medium and more particularly to a recording and reproducing apparatus for stabilizing headtouch by utilizing air flows caused by the rotation of the sheet.
2. Description of the Related Art
Conventionally, in this type of recording and reproducing apparatus mentioned above, when a recording or reproducing head (hereinafter referred to as "head") appproaches a disc rotating at a high speed, stable and sound opposing conditions between the head and the disc will not be maintained due to air flows generated by the rotation of the disc, causing deficiencies such as deteriorating a recording or reproducing capability.
To solve this problem, the efforts have been made to maintain stable and sound opposing conditions between not only the head and the disc but a stabilizer member and the disc by installing the stabilizer member facing the head with the disc put between them to generate air flows by the rotation of the disc.
FIG. 15 shows an illustration of an apparatus of this kind in the prior art.
In FIG. 15, 1 is a flexible disc serving as a recording medium. For example, it is a magnetic disc, and a center core 2 such as of plastic make is attached to the center of the disc 1. The disc 1 is installed to a spindle 3a of a disc rotating motor 3 at a center hole 2a of the center core 2, and is rotated, for example, in the direction of arrow A at a predetermined speed (for example, 3600 rpm for a still video recording or reproducing apparatus). 4 is a recording or reproducing head. For example, it is a magnetic head supported by a head moving carriage 7 (FIG. 16) and is moved in the radial direction of the disc 1 by the moving carriage 7 as shown by arrow B in FIG. 15. In this mechanism, concentric or conical recording track is formed on a recording surface of the disc 1 when recording a signal. As mentioned above, 5 is a stabilizer member installed opposite to the head 4 with the disc 1 put between them to stabilize the part of the disc 1 which goes through the head 4. As mentioned in detail in FIG. 16, the stabilizer member 5 has a concave groove 5c with a rectangular cross section of a predetermined opening width on the opposite surface of the disc in conformity with the moving path of the head 4 in the direction of arrow B in FIG. 15 to evade collision with the head 5, thereby dividing the disc facing surface into an upstream side facing surface 5a and a downstream side facing surface 5b with the concave groove 5c forming the boundary. A back plate 6 having a long hole 6a is installed as required. The head 4 is extruded to the side of the disc 1 through the long hole 6a.
As described above, the stabilizer member 5 is closely faced with the upper side of the disc 1 as shown in FIG. 15, that is, the opposite side of the recording surface. On the other hand, as for the head 4, the extreme end of the head 4 is slightly protruded into the concave groove 5c of the stabilizer member 5, or is protruded to face the recording surface of the disc 1 to keep the same level with the facing surfaces 5a and 5b. The back plate 6 faces the recording surfaces of the disc 1 at a longer distance than the stabilizer member 5. When the disc 1 is rotated in the direction of arrow A in such a condition, the following phenomena will happen: positive pressure is originated between the disc 1 and the upstream side facing surface 5a of the stabilizer member 5, where the disc 1 is pressed down. On the other hand, negative pressure is originated between the disc and the downstream side facing surface 5b, causing the disc 1 to be attracted to the stabilizer member 5 against the rigidity of the disc 1. As the result of this, the downstream side facing surface 5b of the stabilizer member 5 and the disc 1 are liable to contact each other, and when both 5 and 1 contact each other, the situations such as impeding the stabilization of facing conditions between the head 4 and the disc 1 and scratching on the facing surface 5b of the stabilizer member 5 by abrasive materials (for example SiO.sub.2, TiO.sub.2) contained in the binder of the magnetic layers of the disc 1 occur. And in some cases, a servo mechanism can not function properly due to an abnormal load applied to the motor 3 which rotates the disc 1 as the free abrasive meterials torn off from the disc 1 through contacting stick to the scratches on the stabilizer member 5 and deteriorate the surface of the stabilizer member 5. Also, in some cases, the abrasive materials struck to the stabilizer member 5 expedite tearing off of the abrasive material contained in the binder of the magnetic layers of the disc 1 and the torn off abrasive materials also expedite wear of the head 4 by getting into the adjacent of head 4.
All these phenomena are derived from contacting of the disc 1 with the stabilizer member 5 through the negative pressure. As a means to solve the above mentioned problems, an apparatus has been improved to press the disc to the head side with air flows through the rotation of the disc by forming a slant face on the adjacent of the groove of the stabilizer member facing with the disc. (Technical Report, TV Association, TEBS 100-4, pages 20-21, submitted by Matsushita Electric dated Dec. 13, 1984).
According to this method, however, both the upstream side and the downstream side of the grooved part have slant faces, but actually, as the disc deforms by sliding contact with the head, it is necessary to establish the position and the configuration of the slant face in conformity with the deformed configuration of the disc, and merely forming a slant on the stabilizer member is not sufficient to attain the efficiency.
Similar improvement has been proposed in U.S. patent application Ser. No. 838,901 filed on Mar. 12, 1986 (also filed in the United Kingdom, Germany and France) and assigned to the assignee of the present invention, wherein an apparatus has been improved to headtouch with the disc facing the stabilizer member, by forming a slant face for generating positive pressure on the downstream side of the groove of the stabilizer member and by forming the configuration of the groove and the face with suitable angles in conformity with the deformation due to sliding contact of the head with the disc.
However, it is insufficient to get stable and uniform headtouch as the conformity of the slant face with the deformed configuration of he disc for generating positive pressure to press the disc to the head is not enough. That is, there is lack of pressure adjustment in conformity with the difference in rigidity of the disc from the outer circumference to the inner circumference. Therefore, an apparatus capable of gaining stable and uniform headtouch on the whole area of the disc facing the stabilizer member under the upstream side and the downstream side has been expected.